1. Field
This invention relates generally to clamping devices for compressing a tube to obstruct the flow of fluid therethrough. Specifically, this invention relates to clamping devices associated with medical apparatus for closing off tubes through which a fluid, such as blood, may flow, and more specifically to clamping devices which close in response to the detection of a condition in the fluid flowing through the tube.
2. State of the Art
Devices for temporarily clamping resilient tubes to temporarily prevent a fluid from flowing through the tube are well-known. Such clamping devices are often used in association with medical equipment, and are frequently used in connection with medical apparatus which perform circulation of fluids to or from a living body. An example of such a device is disclosed in U.S. Pat. No. 5,062,775 for an extracorporeal support system which operates to circulate blood from a patient through the device and to return the blood to the patient.
Clamping devices take various forms, but typically function by the manually or electrically induced engagement of structure which pinches the tube at a particular location to prevent passage of fluid through the tube. Some clamping devices are connected to means for detecting a specific condition in the fluid which, when the condition occurs, triggers the clamping or unclamping of the tube. For example, it may be desirable to terminate blood flow through a tube if the hematocrit level falls above or below a certain value. For example, if the hematocrit level drops, as sensed by a detection means, an electrical signal is relayed to the clamping device causing it to close off the tube.
Clamping devices currently in use are capable of generally accommodating only those tubes which have a small internal diameter (approximately 1 millimeter to 5 millimeters) and which are very pliant. Further, clamping devices currently in use maintain either a fully opened or a fully closed condition. That is, the tube positioned within the clamp may be either completely uncompressed (open tube) or completely compressed, but may not be partially compressed. Such clamping devices cannot provide incrementally increasing compression of the tube as may be required by some medical procedures. In addition, many clamping devices do not provide means for manually operating the clamping device under emergency situations, such as a power failure, or as may be dictated by medical necessity.
Thus, there remains a need for a clamping device which can accommodate both smaller internal diameter tubes as well as larger internal diameter tubes which are relatively less flexible. There also remains a need for a clamping device which provides for gradual compression of a tube, and which can be manually operated to compress the tube to varying degrees.